The present invention relates to motor vehicles and in particular to a motor vehicle with a lock-up clutch.
Motor vehicles with provisions for extending fuel cut time have been previously proposed. Ganoung (U.S. Pat. No. 5,045,035) is directed to a high-efficiency powertrain. Ganoung teaches a system that includes a high specific output engine coupled to an automatic transmission which, is expanded from four to five forward speed ratios by a novel two-speed torque converter assembly within the transmission. Ganoung teaches this system to exploit the fuel economy potential of modern high specific output engines and more effectively manage the characteristically peaky torque curve of such engines.
Ganoung teaches a lock-up clutch for directly connecting the engine and the transmission in some situations. Ganoung discusses the use of the drive-by-wire control unit to enhance control of the lock-up clutch. In particular, Ganoung teaches that by using the drive-by-wire control unit, the throttle can be prevented from opening immediately following the depression of the accelerator just after the lock-up clutch has been disengaged. This allows a delay during which a smooth reengagement of the clutch can be completed at a fast-idle position of the throttle.
Inokuchi (Japanese Patent Number 2004-322856) is directed to a lock-up controller for an automatic transmission. Inokuchi teaches a method to provide a lock-up controller capable of directly coupling a lock-up clutch, while suppressing shocks, even during deceleration of a vehicle.
Inokuchi teaches an automatic transmission connected with an engine through a torque converter. Inokuchi teaches that when deceleration of a vehicle is started with the torque converter in a non-direct coupling state, the lock-up clutch is changed to a direct coupling state following a shift by the automatic transmission control unit. At the same time, the engine control unit controls the throttle opening so that the throttle opening is reduced at a predetermined rate of change. In particular, the throttle opening is initially open to some finite value and is controlled in a manner that decreases this value over time. This arrangement prevents a sudden reduction of engine speed to allow time for direct coupling of the torque converter to be completed.
The methods of the prior art require time for the engine speed to be iteratively increased or decreased until the desired speed is found for smoothly engaging the lock-up clutch. There is a need in the art for a system and method that addresses this shortcoming, including a system and method for decreasing the amount of time required to reengage the lock-up clutch following a change in the transmission.